Near-resonance electromechanical motor

Abstract

An electromechanical motor according to the present invention has a stator with a drive element consisting of two serially connected bending sections and a central drive pad, for actuating on a body to be moved. The drive element extends parallel to the body. The drive pad and/or the body is elastic. Preferably, the drive pad has a lower stiffness than the body. The elasticity of the drive pad allows an assimilation of a part of the travelling wave energy applied to the drive element. The backbone of the stator is arranged to restrict the drive element from being removed from the body, but at the same time allow the drive element to be translated towards the body and even leave the mechanical contact with the backbone for shorter periods of time. Support means are preferably designed with convex surfaces in order to allow self-centering of the different parts of the motor.

What is claimed is:  
     
       1. An electromechanical motor, comprising: 
       stator, having a driving element and a backbone portion;  
       body to be moved in a main displacement direction by said driving element;  
       resilient means arranged to apply a normal force between said driving element and said body;  
       said driving element in turn comprising:  
       a first and a second bending section, generally elongated along said main displacement direction, connected in series to each other in said main displacement direction;  
       said first and said second bending section each having a first and a second portion interconnected along said main displacement portion and essentially parallel to a drive surface of said body;  
       said first portion being an active electromechanical element presenting a dimension changeability in said main displacement direction; and  
       drive pad arranged to actuate on said body and arranged at a point close to the center of said driving element;  
       at least one of said drive pad and said body being elastic.  
     
     
       2. The electromechanical motor according to  claim 1 , wherein said drive pad has a stiffness that is lower than a stiffness of said body. 
     
     
       3. The electromechanical motor according to  claim 1 , wherein said drive pad has an elasticity allowing for assimilating a non-negligible portion of an energy of a travelling wave applied to said driving element. 
     
     
       4. The electromechanical motor according to  claim 1 , wherein said drive pad has an elasticity restricting a time of compression when a travelling wave passes to less than half a cycle time of said travelling wave. 
     
     
       5. The electromechanical motor according to  claim 1 , wherein said drive pad is positioned at the center of said driving element, with respect of said main displacement direction. 
     
     
       6. The electromechanical motor according to  claim 5 , further comprising attachment means between said drive element and said backbone arranged in vicinity of an outer end of a respective one of said bending sections, restricting substantial translational motion of said driving element in relation to said backbone. 
     
     
       7. The electromechanical motor according to  claim 6 , wherein said drive element is substantially symmetric around said drive pad. 
     
     
       8. The electromechanical motor according to  claim 6 , wherein said attachment means comprises supporting means with a protruding portion having a convex surface supporting against a counter surface. 
     
     
       9. The electromechanical motor according to  claim 8 , wherein said protruding portion is comprised in said drive element and said counter surface is comprised in one of said backbone and said resilient means. 
     
     
       10. The electromechanical motor according to  claim 9 , wherein said protruding portion has a half-spherical shape. 
     
     
       11. The electromechanical motor according to  claim 8 , wherein said protruding portion is comprised in one of said backbone and said resilient means, and said counter surface is comprised in said drive element. 
     
     
       12. The electromechanical motor according to  claim 6 , wherein said attachment means comprises means for restricting translational motions of said drive element in said main displacement direction. 
     
     
       13. The electromechanical motor according to  claim 12 , wherein said means for restricting translational motions of said drive element in said main displacement direction are attached to said drive element at said interconnection between said first and second portions or closer to said body than said interconnection between said first and second portions. 
     
     
       14. The electromechanical motor according to  claim 12 , wherein said means for restricting translational motions of said drive element in said main displacement direction are attached to said drive element at solder pads on said drive element. 
     
     
       15. The electromechanical motor according to  claim 1 , wherein said second portion is an active electromechanical element presenting a dimension changeability in said main displacement direction. 
     
     
       16. The electromechanical motor according to  claim 1 , wherein said second portion is a non-electromechanically active portion. 
     
     
       17. The electromechanical motor according to  claim 16 , wherein said second portion is a metal sheet. 
     
     
       18. The electromechanical motor according to  claim 1 , wherein said first and second bending sections are connected via a passive portion, to which said drive pad is attached. 
     
     
       19. The electromechanical motor according to  claim 1 , wherein said body has negligible bending vibrations in a operation frequency range of said electromechanical motor. 
     
     
       20. The electromechanical motor according to  claim 1 , wherein said body has a surface roughness on a surface facing said drive pad that is at most in the same order of magnitude as the movement of said drive pad perpendicular to said main displacement direction. 
     
     
       21. The electromechanical motor according to  claim 1 , wherein said body has a surface facing said drive pad having a cylindrical shape. 
     
     
       22. The electromechanical motor according to  claim 1 , wherein said resilient means has a spring force varying less than 10% within an allowed range of tolerances of said motor. 
     
     
       23. The electromechanical motor according to  claim 1 , wherein said resilient means has a general C- or U-shape, contacting said body and said backbone or drive element only at contact portions on opposite sides of said C- or U-shape. 
     
     
       24. The electromechanical motor according to  claim 23 , wherein said contact portions comprise protrusions having convex surfaces. 
     
     
       25. The electromechanical motor according to  claim 24 , wherein said body, backbone or drive element comprises dimples or holes for receiving said protrusions. 
     
     
       26. The electromechanical motor according to  claim 23 , wherein said contact portions support against protrusions at said body and/or said backbone having convex surfaces. 
     
     
       27. The electromechanical motor according to  claim 24 , wherein said contact portions comprise dimples or holes for receiving said protrusions. 
     
     
       28. The electromechanical motor according to  claim 1 , wherein said resilient means is comprised in said body. 
     
     
       29. The electromechanical motor according to  claim 1 , further comprising means for inducing travelling waves in said drive element, said travelling waves having a frequency near a resonance frequency of said drive element. 
     
     
       30. The electromechanical motor according to  claim 29 , wherein said resonance frequency of said drive element is a resonance frequency of a bending mode. 
     
     
       31. The electromechanical motor according to  claim 30 , wherein said bending mode has an odd number of nodes. 
     
     
       32. An electromechanical motor, comprising: 
       stator, having a driving element and a backbone portion;  
       body to be moved in a main displacement direction by said driving element;  
       resilient means arranged to apply a normal force between said driving element and said body;  
       said driving element in turn comprising:  
       a first and a second bending section, generally elongated along said main displacement direction, connected in series to each other in said main displacement direction;  
       said first and said second bending section each having a first and a second portion interconnected along said main displacement portion and essentially parallel to a drive surface of said body;  
       said first portion being an active electromechanical element presenting a dimension changeability in said main displacement direction; and  
       drive pad arranged to actuate on said body and arranged at a point close to the center of said driving element;  
       whereby one of said backbone and said resilient means is arranged to restrict translational motion of said driving element away from said body perpendicular to said main displacement direction, but allow translational motion of said driving element towards said body perpendicular to said main displacement direction.  
     
     
       33. The electromechanical motor according to  claim 32 , wherein contact means between said one of said backbone and said resilient means, and said drive element comprises a protruding portion having a convex surface supporting against a counter surface. 
     
     
       34. The electromechanical motor according to  claim 33 , wherein said protruding portion is comprised in said drive element and said counter surface is comprised in said one of said backbone and said resilient means. 
     
     
       35. The electromechanical motor according to  claim 34 , wherein said protruding portion has a half-spherical shape. 
     
     
       36. The electromechanical motor according to  claim 33 , wherein said protruding portion is comprised in on of said backbone and said resilient means, and said counter surface is comprised in said drive element. 
     
     
       37. An electromechanical motor, comprising: 
       stator, having a driving element and a backbone portion;  
       body to be moved in a main displacement direction by said driving element;  
       resilient means arranged to apply a normal force between said driving element and said body;  
       said driving element in turn comprising:  
       a first and a second bending section, generally elongated along said main displacement direction, connected in series to each other in said main displacement direction;  
       said first and said second bending section each having a first and a second portion interconnected along said main displacement portion and essentially parallel to a drive surface of said body;  
       said first portion being an active electromechanical element presenting a dimension changeability in said main displacement direction;  
       said second portion being a passive element; and  
       drive pad arranged to actuate on said body and arranged at a point close to the center of said driving element.  
     
     
       38. The electromechanical motor according to  claim 37 , wherein said second portion of said first and second bending sections comprises a metallic sheet. 
     
     
       39. The electromechanical motor according to  claim 38 , wherein said second portion of said first and second bending sections further comprises a flexible printed circuit board. 
     
     
       40. The electromechanical motor according to  claim 38 , wherein said metallic sheet also forms said drive pad.